Networks can be comprised of a multiplicity of network devices such as servers, routers, hosts, switches, repeaters, hubs, encryption devices and backup devices such as media libraries.
In many systems, data may be sent over a network from multiple hosts on the network to a library for storage. Such hosts may include computers, servers or other devices. In many instances, the data is routed to the library through a multiplicity of network devices which may include one or more switches, routers, servers, hubs, encryption devices or other network devices. A host or other device may also request data from a library and this data may be routed to the host or other device through the network.
One example of a library commonly used for data storage is a magnetic tape library. A magnetic tape library can comprise components such as tape cartridges (containing magnetic tape), robots, tape slots and tape drives. A typical magnetic tape library contains multiple cartridge slots in which tape cartridges can be stored. Tape cartridges, commonly referred to as tapes, are physically moved between cartridge slots and tape drives by a robot. The robot is controlled by commands received from the host devices on the network. When data is to be written to or read from the library, a host device determines which cartridge slot contains the tape cartridge that is to be written to or read from. The host device then transmits a move-element command to the robot and the robot moves the tape cartridge to a tape drive which reads the desired data from the tape cartridge.
A tape drive in a library reads from or writes to magnetic tape contained in a cartridge utilizing a sensor which may comprise a read head and a write head. In one embodiment of a drive, magnetic tape is pulled past the sensor comprising the read head and the write head such that the read head can read data from the tape and the write head can write data to the tape.
Reading and writing to a cartridge inherently causes the degradation of the tape comprising the cartridge because the tape is pulled past the read and write heads. Pulling the tape past the read and write heads may strain the tape and the tape may collide with the read or the write heads at read or write speed. Especially deleterious to tape life is starving a drive of data to write to a tape. In particular, if data is received at a drive at below the drive's ability to write data (i.e. at below the drive's streaming rate), then the movement of magnetic tape may have to be slowed or reversed in order to write data with the necessary density, wearing the tape. Such back and forth pulling of tape past the read and write heads of a drive is referred to as “shoe-shining” and has the potential to accelerate tape degradation. Consequently, bottlenecks or other decreases in data transfer rates caused by network devices can have a deleterious effect at the library.